Detecting the presence and concentration of different chemical species using amperometry is a very well known technique. Basically, a voltage appropriate for the species to be detected is applied between two electrodes in communication with a fluid possibly containing that species. The voltage is selected which is sufficient to cause oxidation or reduction of the species to be detected but ideally not any other species in the fluid. The resulting current between the electrodes in response to the applied voltage can then provide an indication of the presence or concentration of the species to be detected. In coulometry the total current over a period of time is measured. In the present application “amperometry” will be used to include methods such as coulometry or voltammetry. Descriptions of amperometry and methods, including selection of the appropriate voltage, are widely available in references including the following and references cited therein: (i) Handbook of Ion Chromatography, Third Completely Revised Edition, 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, ISBN: 3-527-28701-9 (see section 7.1.2 “Amperometric Detection”); (ii) “Pulsed Amperometric Detection Based on Direct and Indirect Anodic Reactions: A Review”, Electroanalysis, 1 (1989) 189-197; (iii) “Development of Instrumentation for Amperometric and Coulometric Detection using Ultramicroelectrodes”, J. Braz. Chem. Soc., Vol. 19, No. 1, 131-139, 2008.
Amperometry has been used to detect a large variety of organic species. Additionally, amperometry has also been used to detect chlorine in aqueous compositions, such as described in “Comparison of On-line Chlorine Analysis Methods and Instrumentation Built on Amperometric and Colorimetric Technologies”, 2009, available from the American Water Works Association, and French patent FR2778463.
In cases involving the oxidation of aliphatic organic compounds at an anode, where the electrolyte is in direct contact with the anode and cathode, it has been recognized that the anode can become fouled—see for example “Liquid Chromatography with Pulsed Electrochemical Detection at Gold and Platinum Electrodes”, Analytical Chemistry, Vol. 62, No. 10, May 15.1990. In that situation a technique known as pulsed amperometric detection has been used in which a reading potential is applied, followed by a large positive potential to oxidatively desorb adsorbed hydrocarbons, then followed by a large negative potential to cathodically dissolve oxides.